Wiring the relay to the compressor clutch will make the fan work when you are at highway speed too. No problem, but you could use an original equipment thermostat switch that goes in the lower radiator hose.

It will help with both the temp and AC.
You do need a relay.

You want a relay with 2 87 termnals if possible, if you can only find one with 87 and 87a use the 87 terminal. Look for 30A load capacity at least, these fans draw a lot starting up, and quite a bit just running.

Power to terminal 30
Fan from terminal 87
signal from AC conpressor wire to either 85 or 86
Ground from either 85 or 86 (it's just an electromagnet polarity doesn't matter)

Enjoy the cooling.
--
Dave Shannon
Spring Valley, California
'67 1800s
'73 1800ES
'88-240
my pages

you can go to the junk yard and pull one of those metal, cube-shaped relays from a 240. look behind the center console, and on an early volvos (84 & earlier) there should be a relay sitting on the driver's side of the engine bay.

also, in the 240s, in my 86, grab the white car fuse on the driver's side wall of the engine bay. that will be your fuse holder.

mount the relay close to the fan. i put my fan relay & fuse on the power strip bar on the driver's side of the engine bay.

there are some wiring diagrams around, but i can't access the site i used at the moment.

regards,
byron golden
86 245
92 245

Go to http://www.nostalgicairparts.com/RELAYS%20&%20THERMOSTATS.htm

and order a Bosch relay and plug. wire it up so it triggers from the AC clutch wire or the wire going to it on either side of the pressure switch. do a google search for the bosch relay to find the pin out schematic.
The pusher fan won't work for primaary cooling but will help a bunch with the ac on especially in heavy traffic.
--
-------Robert, '93 940t, '90 240 wagon, '84 240 diesel (she's sick) , '80 245 diesel, '86 740 GLE turbo diesel, '82 Mercedes 300SD for sale